1. Field of the Invention
This invention relates to precast traffic barriers and retaining walls for use in highway construction. More specifically, the present invention relates to a combination of a precast concrete traffic barrier and a precast retaining wall and a method of constructing the traffic barrier on the top face of the retaining wall.
Traffic barriers are used on roads to keep a moving vehicle from crossing into the path of oncoming traffic or from driving off the roadway. The traffic barrier is especially useful on elevated or split-level roadways, such as bridges, entrance ramps, or access roads to highways, to prevent a vehicle from driving off the road onto a lower level roadway. These elevated roads are often formed by cutting through a hill or by piling earth or soil onto metal reinforcements to form a laterally stabilized composite earth structure to support the road. Either method of construction may result in a wall face which needs to be supported by a retaining wall. If this retaining wall is close to the road surface there is a need for a traffic barrier which can be anchored on top of the retaining wall. The wall, of any height, defines a lengthwise horizontal beam for anchoring the barrier.
Retaining walls may be cast-in-place, built from blocks placed one on top of the other, or may be prefabricated panels. All retaining walls are designed to protect the earth slope from slides due to weather erosion.
Construction of a traffic barrier on top of and along a retaining wall may be cast-in-place so as to be an integral part of the retaining wall. However, this construction method requires forms to be constructed by workmen on scaffolding. Hand construction of the forms and pouring of concrete is slow and labor intensive. Thus, there is a need for a more efficient method of constructing a combination traffic barrier and retaining wall.
2. DESCRIPTION OF THE PRIOR ART
Basic traffic barriers separating two lines of vehicular traffic are not new in the art. U.S. Pat. No. 3,678,815 issued to Younker discloses a concrete traffic barrier which may be used in forming bridge guard rails, median barriers, and the like. The Younker barrier includes a pair of identically shaped shells which are bolted together leaving a void into which concrete is poured to form a core of solid material. U.S. Pat. No. 4,435,106 issued to Forster et al. discloses a traffic barrier which may be used to separate a roadway. The Forster traffic barrier may be cast-in-place through the use of forms to construct a solid concrete barrier which rises from the roadway edge outwardly first gently and then more strongly and then spaced below an overhanging guiding mechanism. A steep convex rise follows the gentle rise and transfers under the guiding mechanism into a flattened area.
Combining steel and concrete in a traffic barrier was disclosed in U.S. Pat. No. 4,496,264 issued to Casey. Casey discloses a barrier structure comprised of a number of spaced apart inline vertical I-beam sections embedded in a roadway and having secured to the I-beams a number of form plates having a pair of downwardly and outwardly diverging pair of legs and a pair of upwardly diverging extending arms. Reinforcing rods are extended through aligned holes in the plates and side panels are connected to the panels. Concrete is poured down through the open top of the structure completely encasing the I-beams, panels, and reinforcing rods. The concrete bonds the side panels and a capping piece is pressed down into the concrete to form the steel and concrete traffic barrier.
Constructing concrete traffic barriers with precast concrete was first patented by Smith in U.S. Pat. No. 4,059,362. Smith discloses a highway traffic barrier composed of precast, reinforced concrete barricades which are joined together. The alignment with each barricade is accomplished through the use of a horizontally and vertically tapered, vertical tongue-and-groove arrangement. This tongue-in-groove arrangement is molded onto the ends of each barricade with the wider portion of the taper at the bottom to facilitate the removal of one piece of the traffic barrier within an installation. The Smith barricade though is designed to be a highway median barrier and cannot be secured to a retaining wall.
A precast barrier design which can be used an retaining walls is disclosed in U.S. Pat. No. 4,494,892 issued to Wojciechowski. This design makes use of an interior channel of the barrier which directly mounts the top edge of the retaining wall to partially support the barrier element. Concrete fill must be used between the top edge of the wall face and the internal face of the channel to ensure that gaps are eliminated. If gaps were allowed to exist, then debris and water could penetrate through the gaps and accumulate behind the wall face. The projecting anchoring rods extend either transversely into a lateral cast in situ counter apron under the roadway surface or downwardly into the earthen support of the roadway. These projecting anchoring rods stiffen the barrier and wall while counterbalancing vehicle impact forces.
Another known precast traffic barrier is U.S. Pat. No. 4,348,133 issued to Trent disclosing a precast polymer concrete shell which is placed at the construction site then filled with hydraulic concrete or other ballast through filling holes on top of the shell. However, the shell cannot be placed on a retaining wall since the shell must be entirely placed on the road or bridge surface.
A method of joining precast concrete barriers to substantially flat roadway surfaces is disclosed in U.S. Pat. No. 4,605,336 issued to Slaw. This design uses a tunnel-like opening extending longitudinally through the bottom of the deck. The first part of the opening is comprised of an inwardly flaring void immediately followed by an outwardly flaring void. This sequence repeats itself throughout the length of the parapet. Parapet reinforcing bars are cast within the parapet and extend horizontally through each section of the inwardly flaring voids. U-shaped deck reinforcing bars are cast within the concrete deck and extend upwardly within each section of the outwardly flaring voids. A locking bar is inserted through the voids above the parapet reinforcing bars and below deck reinforcing bars. Pressure pumped concrete grout is then forced into grout inlet holes until the entire length of voids is filled with grout. One problem with this design is that it can only be used on a substantially flat roadway and the alignment of the precast barrier and roadway must be precise to insure that the U-shaped rods are inserted into outwardly flaring voids.